\begin{pspicture*}(-5,-0.7)(5,0.7)
\rput[l](1,0){$y$}
\rput[r](-1,0){$x$}
\pscurve{->}(-0.8,0.1)(0,0.2)(0.8,0.1)
\rput[b](0,0.3){$f$}
\pscurve{<-}(-0.8,-0.1)(0,-0.2)(0.8,-0.1)
\rput[t](0,-0.3){$f^{-1}$}
\end{pspicture*}